Furnace grate structure



June 4, 1935.l i J, S BENNETT A 2,003,423

FURNACE GRATE STRUCTURE Filed July 28, 1931 3 Sheets-Sheet l June 4, 1935.

J. S. BENNETT F'URNACE @RATE STRUCTURE A Filed` July 28, 1951 3 Sheets-Sheet 2 Emme @E T935. J. s. EENNETT v2,003,423

FURNACE GRATE STRUCTURE Filed July 28, 1931 3 sheets-Sheet s E Y( r l yl l 4. /ZJ L Patented June 4, '1935 PATENT OFFICE 2,003,423 e FURNACE GRATE STRUCTURE Joseph S. Bennett,l Merion, Pa., assignor to YAmerican Engineering Company, Philadelphia, Pa., a corporation of Pennsylvania Y Application July 28, 1931, Serial No. 553,622

10 Claims.

This invention relates to improvements in furnace grate structures and, while applicable Vin principle to other types of grates and stokers, nds an applicationof particular value in the extension grates of multiple-retort, underfeed stokers.

One object of my invention is to provide a grate structure of novel and generally improved design and construction.

Another object of the invention is to provide a novel form of grate construction, applicable to mechanical stokers, in which the 4fuel-sup porting surface is composed of .a plurality of relatively small readily replaceable elements.

A still further object 'is to provide a stoker extension or like grate wherein the passages for combustion air to the fuelbed are substantially free from any tendencyto clog from accumulation of siftings lor from other causes.

Still another object of the invention is'to provide a stoker extension or like grate wherein the passages for combustion air in any part of the grate may be readily modied to meet any special condition.

Another object is to provide Va grate of the stated type wherein prcvisionis made for free expansion of those portions oi' thegrate exposed to the fuel. ,Y l y f Still another object-is to provide a stokerextension vor like grate including a-plurality of securely anchored, replaceable fuel-supporting i" elements wherein said elements are free toY ex pand both laterally and in the longitudinal direction.

or all of said grate is renewable without affecting the other parts of the Stoker structure. v

Still another object of the invention is to-pro- Vide a mobileextension grate or equivalent stoker member comprising a suitably formed` metallic framework and a plurality of elements removably mounted in said framework and forming the effective fuel-surface.

A further object of the invention is to provide in a Stoker grate member of the stated character a novel form of detachable facing element including means for passing combustion air through the grate to the fuel-bed.

A further object of my invention is to provide la metallic framework which will' so support nonfor securing the facing elements or blocks in the supporting framework of the grate, and in Various other structural details hereinafter set forth and illustratedv in the attached drawings, in which: Y y v a Fig. 1 is a longitudinal section showing a part of the lower or overfeed section of a multiple retort underfeed stoker and one section of Y the extension grate in side elevation;Y Fig. 2 is a rear elevation ofthe portion Stoker shown in Fig. 1

Fig. 3 is a top plan view of one ofthe extension grate sections; f

Fig. 4 is a side elevation'. and partial sectional View of the extension grate vsection shown in 15` Fig. 3; n Fig. 5 is a top plan view of the top cross bar Vof one of the extension grate sections;

Fig. Gis a rear elevation ofthe said top bar; Fig. 7 is a section on the line 1 1, Fig; 6; 20 Fig. 8 is a View in'perspective of one ofthe lower cross bars of the-extensiongrate sections; Fig. 9 is a top plan View of the lower` rear portion of one of the extension grate sections;-

Fig. 10 is asection on the line lll-I0, Fig. 9; 25 Fig. v11 is a View in perspective of` one of the tie plates which unite the forward and rear partsof the individualfextension grate sections; Fig. 12 is a View in perspective of one of the facing blocks; and Y 1 Fig. 13 is a view in perspective of one of the lower terminal blocks of the extension grate.

With reference to Fig. 1 of theA drawings, y1| is the dead plate positioned at the lower end of the inclined retorts ofI anunderfeedstoker of a wellV V35 known type, over which dead plate. the fuel dis@ charged from the retorts passesto an extension grate 2. This extension grate terminates at-ts lower end in an ash pocket 3,V the forward wall of which is indicated atl. In `the presentin'f 40 stance, the entire rear or overfeed portion of the Y stoker including the dead plate fl, the extension grate 2 andthe lower grate 4, is carried at ltheV lower end of a series of inclined beams, the Vup'- per edge of one of which is indicated at 5. and 45 K of the 1o grate units is effected by suitable actuating mechanism through the medium of a rod or rods 'I connecting to the forward or inner sides of the said units and extending forwardly of the stoker below the dead plate I. Reciprocation of the extension grate units results in a movement of the fuel and the fuel residue or ash into the ash pocketB, the movement of the extension grate being in timed relation with the fuel feeding devices of the overfeed section of the Stoker.

As illustrated in the drawings, each of the extension grate units comprises a forward section II and a rear or lower section I2. The forward section II comprises a pair of side plates I3, I3 which are united by a plurality of transverse bars I4 and I5, said plates and bars forming in effect an open frame. Each ofthe plates I3 is formed with forward and rear substantially Vertical edges IB and I'I and a horizontal bottom edge I8. IIfhe upper edge I5 of each of the plates inclinesupwardly from the top Vof the rear edge I,'I and terminates Vin a substantially horizontal ltop edge portion 2|. The transverse bar I5 extends between the plates directly below the upperwedge portion 2I, and the bars I4 are secured in spaced relation to each other and to the upper bar I5 immediately below the inclined edge I9, thereby forming in effect an inclined series substantiallyvparallel to said edge. y

The top bar I5 is illustrated in detail in Figs. 4 to 7 inclusive As therein illustrated, this bar comprises end'flanges' 22 which in assembly lie flat against the inner faces of thev side plates I3 and which provide means for bolting the bars to the plates, the bolts being indicated in the assembly view of Fig. 4 by the reference numeral 23. The bar I5 further comprises a horizontal web 24 lwhich extends transversely between the inner faces of the end flanges 22,' which web in its` mid section is'formed with a substantially cylindrical boss 25 forming a'socket for reception of the end of the actuating rod 1. The web 24 at its forward edge'is flanged vertically, the said flange being indicated by thereference numeral 26, see Fig. 7, this flange serving for longitudinal reinforcement of Athe bar; and at its rear edge the web 274 has a similar flange 21 which at its upper edge is provided with a plurality of inturned apertured lugs 28 functioning for a purpose hereinafterV set forth. l

One of the bars I4 is illustrated in Fig. 8.

These bars are of a modified T-section, the flange 3| constituting one leg of said T assuming a vertical position, and the other lleg 32 extending to-v wards the forward side ofthe extension grate. At the ends, the bars I4 are provided'with transverse flanges 33 which present fiat surfaces for abutment with the inner faces of the plates l 3 and which in the present instance are apertured for reception of bolts 34 by means of which the said bars are secured to the side plates.

The rear or lower section I2 vconsists inthe present instance of an integral substantially triangular member including side plates 36 and a plurality of cross bars designated respectively in 9 by the reference numerals 31-38-39-4 I. These cross bars as shown in Fig. 10 differ from each other as to cross sectional form, but it will be noted that each of the bars 3'I-38-39 has an upstanding flange 42 and a substantially vertical rear lface 43, these faces inthe present instance being provided with a plurality of Vertical ribs 44 Yfor a purpose'hereinafterset forth. The lower cross bar 4I is relatively flat, but is also provided at its rearward edge with an upstanding flange "plates 36 ofthe section I2.

45. The forward edges of the side plates 35 of this lower section are adapted to abut the rear edges Il of the side plates of the section II, the two sections II and I2 being secured together through the medium of tie plates 46 which overlap the adjoining edges of the side plates and are secured against the inner surfaces of the plates by means in the present instance of bolts 4l. It will be noted also that the rear edges Il of the side plates of the section II are formed with a projecting flange 48, while complementary flanges 49 are provided on the forward edges of the side These flanges form an overlapping joint between the side plates of the two sections.

In assembly, the Various elements described above form a substantially rigid open framework of approximately triangular form with a plurality of transverse bars extending in an inclined series between the sides along the upper inclined edges of the plates. f

In conjunction with the frame described above, I provide a plurality of blocks which are adapted to be mounted detachably on the frame to form blocks 5I shown in Fig. 12 consist of a substantially rectangularV body portion having at the front and on the under side a depending rec; At both sides of the mem# ber 52, the under side of the block is cut away to tangular portion 52.

form inclined planes 53 which extend from the bottom surface of the block forwardly and upwardly and terminate slightly below the top front edge. With the block mounted in a substantially horizontal position, the inclination of the planes 53 corresponds with the inclination of the upper edge of the side yplates of the extension grate section. The block 5I is provided on the two sides and bottom surface and in the front and rear faces of the depending portion 52 with grooves 54, the grooves in the said side and bottom faces extending from the rear face of the block to the inclined planes 53, and the grooves 55 in the front and rear faces of the depending portion 52 extending vertically the entire length of the faces which they occupy.

The blocks 56 shown in Fig. 13 are similar in general form to the blocks 5 I but differ therefrom in that they include at the rear under side a depending portion 5'1. These blocks like the blocks 5I include the inclined surfaces 58 corresponding to the surfaces 53 of the block 5I, and intermediate these inclined faces a depending substantially rectangular portion 53. Intermediate the depending portions 51 and 59 is a transverse recess 5I. These blocks like the block 5I are provided in their side faces with grooves 62 and in the forward face of the depending portion 59 with grooves 63.

The blocks 56 are adapted to be mounted as illustrated in Fig. 4 upon the lower cross bars 4I, the flange 45 of the cross bar entering the recess vISI of the blocks, and the forward face of the section.

The blocks 5I are mounted in similar series however, are direct abutting relation to the vertical rear faces of the cross bars, and the latter 'top of the underlying block, while the forward face of the depending section 52 aouts the vertical surface of oney of the cross bars. The rear lower edge of the depending portion 52 Vlies behind 'and below the top of the upwardly extending Vflange of the next lower` cross bar, so that these blocks are securely locked in position in the structure. any of the blocks, however, may be withdrawn from the structure by tilting the rear end upwardly sufficiently to clear the depending portion 52 lfrom the underlying cross bar and the forward upper edge of the next lower block. YIn order to prevent accidental displacement of the uppermost series of blocks, I provide a cap plate 65 which rests upon the upper edges of the side plates i3 and extends rearwardly over the'said series of blocks. rlhis cap plate is secured in position by bolts which pass downwardly through the lugs 2S of the top cross bar l5. A

It will be noted that the grooves in the faces of the blocks 5i and 5S together with 'the ribsv projecting from the rear faces of the lower group of cross bars provide air channels for passage of air from below the grate to the fuel-bed. These grooves also provide for free circulation of air around the blocks to air-cool the latter and to prevent destruction thereof by heat. Y All of the grooves extending to the fuel-bed terminate in vertical surfaces of the blocks so that there is no tendency for the air passages to clog from accumulation of ash siftings therein, and the flow ir around the blocks to the fuel-bed is maintained continuously at maximum efficiency. i Also, the blocks being arrange in true vertical series, there are no pockets in which siftings may accumulate. Destruction of the blocks due to burningis thus largely avoided and the efficiency of combustion in this Y part of the furnace is at a maximum. By increasing or` decreasing the depth of the air grooves in oneY or more of the bl cke, the iicw of air to any part of the related portion of the fuel-bed may be varied to meet any special condition.

By forming the grate of a plurality of transversely arranged units, and by employing for the fuel-supporting portions of these units a plurality of facing'bloclrs securely anchored yet sufficiently loosely assembled toy permit substantially expansion in all directions, the diiculties experienced inthe prior types of grate due to excessive expansion are eliminated. There is no binding from this cause between the units, nor between i locks of the transverse and vertical series of the individual units, nor between the blocks and their supporting frames. Where replacements are required, therefore, the individual blocks are readily withdrawn and new blocks inserted.

The construction also provides for utilizing in those portions of the grate where excessive burningV is likely to occur, materials especially suited to withstand the high temperature conditions. The lower transverse series of blocks, for example, might be formed of silicon carbide or other high refractory material; or the entire group of blocks might be so constituted.

The extension grate as described above has exceptional strength and durability. The pressures exerted by the fuel-bed as the grate sections are advanced are in a substantially straight line from the rear to the forward faces of the blocks 5l and 55. The forward faces of the blocks,

fstrains.

any suitable refractory or heat-resisting mate- -bustion is employed. `is of particular significance in connectionk with Vof elements having amply' reinforce the blocks' against all normal The blocks 5l and 5t may be formed of rial, such for exampleas cast iron, or silicon carbide, capable ofwithstanding the compressive forces normally applied thereto.` The removable feature ofthe facing blocks is of great importance by reason of the fact that if one or more of these blocks is destroyed by excessive overheating or from other cause, they may be readily and rapidly l replaced without dismounting any part of the grate as a whole.V The framework of the grate Ybeing nowhere in direct contact with the fuel is not subject to destructive heat action. These factors are of particular value in conjunction with the extension grates of underfeed stokers of the type set forth, since considerable difficulty has been experienced in maintaining these grates in continuous operation. These grates constituting a major part of the overfeed section of the Stoker, and being in direct contact with the incandescent fuel, are subject to burning particularly where,`v

asis becomingv general practice, preheatedfcomstolfrer extension gratos, as set forth above, it may find useful application in principle to Vother furnace grate structures; and there are to be no Vimplied limitations beyond those specifically imposed by the terms cf the claims. l

l claim: l. A Stoker grate structure comprising a frame including a plurality ofV transverse bars arranged .in an inclined series, and a plurality of facing elements mounted on saidbars and forming Ythe effective fuel-supporting surface' of the grate, each of saidY elements having a faceabutting an opposed face of oneof the bars and having also a depending portion normally disposed'i'n sub-r stantially abutting relation with the next lower bar of the series whereby accidental displacement ofthe elements from the frame is prevented.

2. A furnace grate structure comprising a plurality of transverse bars arranged in anr'incline'd serie-,sa series of facing elements supported by andinterl'oclied with the lower of said bars, each Y a forward Vface abutting lan Y opposed facey ofthe last mentioned elements having a 'rear projecting portion seated on( thetop of, theelements rst named and having a forward face abutting one of the cross'fbars of saidinclined series, each of the last-named elementsA having a depending portion disposed in substantially abutting lrelation bars of the series constituting a backing for one of the series of said elements. Y

s. A Stoker extension grate unit comprising a pair of side plates and an inclined series of cross bars connecting said plates, a plurality of series of facing elements supported on said bars, each While the construction v next higher bar,l anda "second series of facing elements, Veach of .of said elements having a forward surface in abutment with one of the bars and a rearward surface disposed in substantially abutting relation with an underlying bar, the latter surface being disengageable from the said underlying bar by elevation of the rear end of said element to permit removal of the element from the structure.

5. An extension grate for mechanical stokers comprising vertical side plates, and a plurality of bars extending transversely between and uniting said plates, said bars being arranged in an inclined series, a plurality of blocks of refractory material supported in horizontal rows and extending between the adjacent bars, each of said blocks having a forward surface abutting one of said bars, and a depending portion extending below the top of the next lower bar of said series whereby said blocks are detachably retained in the framework, and each of said blocks having a rearwardly extending portion overlying and supported on the top of a lblock of the immediately underlying row, said rearward extensions producing an effective fuel-supporting surface of stepped formation. Y

6. An extension grate for mechanical stokers comprising an inclined series of spaced horizontal bars, a plurality of blocks of refractory material mountedupon said bars in .superimposed horizontal rows, each of said blocks having a forward surface abutting one of said bars,V and a depending portion extending below the top of the next lower bar, and each of said blocks also having a part extending rearwardly from said depending portion and ndinga support upon the upper surface of the blocks of the immediately underlying row, said blocks forming an effective fuel-supporting surface.

7. A furnace grate structure comprising a plura-lity of series of elements arranged in superimposed series and constituting the effective fuel supporting surface of the grate, each of said elements having a substantially vertical forward face, and a depending portion, cross bars arranged in inclined series for supporting said eledepending from said body portion having substantially vertical side, front and rear faces, the front face of said projection being substantially flush with the front edge of said body portion, an inclined supporting surface on said body portion extending laterally from each side face of said projection, substantially longitudinal ribs on the side and bottom' surfaces of said body portion and substantially vertical ribs on the front face of said projection.

9. A grate block adapted for assembly with similar blocks in side by side relation upon a vframework of a reciprocable extension grate,

said block comprising a substantially rectangular body portion having a substantially vertical fuel feeding surface, a substantially horizontal fuel supporting surface, and substantially vertical side surfaces, a substantially rectangular projectionY depending from said body portion and extending substantially from the front edge thereof to a point intermediate said front edge and'said fuel feeding surface, said projection having substantially vertical side, front and rear faces, a second projection depending from said body portion in spaced relation with said rst mentioned projection forming a recess therebetween, a downwardly inclined supporting surface disposed on each side of said rst mentioned projection, substantially longitudinal ribs on the side surfaces of said body portion and substantially vertical ribs` on the front face of said first mentioned projection.

10. An extension grate for stokers comprising in combination, a plurality of transverse rows of refractory blocks arranged in superimposed stepped relation, and a framework for supporting said blocks, said framework including spaced side members, and supporting means disposed between said side members, said supporting means including upper, lower, and intermediate transverse members, the lowermost of said transverse members comprising a substantially flat portion and a vertical ange extending upwardly therefrom, means provided on each of the lowermost rows of blocks adapted in assembly to interlock with said flange whereby said blocks are anchored in position, interlocking means provided on the other of said transverse rows of blocks and the intermediate of said transverse members, retaining means detachably secured to the upper of said transverse members and overlying the uppermost of said rows of blocks for preventing vertical displacement of said blocks, and means disposed between adjacent blocks defining passages for draft air.

JOSEPH S. BENNETT. 

